Alcoholism is responsible for one third of preventible loss of life in the United States. About 50-60% of the predisposition to develop alcoholism is genetically determined, and both permissive and protective genes have been identified. Two gene variants strongly associated with protection against alcohol abuse and alcoholism modify the metabolism of ethanol. These genes code for enzymes that either increase the production or reduce the elimination of acetaldehyde, the first product of ethanol metabolism. A dominant negative allele of aldehyde dehydrogenase (ALDH2) found in East Asians codes for an inactive ALDH2*2 that does not metabolize acetaldehyde efficiently. This results in increased levels of circulating acetaldehyde and in an aversive reaction that protects against alcoholism by 65 to 95%. Another protective gene variant ADHIB*2 codes for an alcohol dehydrogenase with a high activity in oxidizing ethanol into acetaldehyde. This inborn protection against alcoholism can reach 50-60%. Disulfiram, an ALDH inhibitor used in the treatment of alcoholism has two main drawbacks that have reduced its use; marked toxicity due to nonspecific action and poor patient compliance with daily intake. Studies in this application test the hypothesis that a reduction ofALDH2 gene expression or ADH gene transduction decrease voluntary ethanol intake in rats, thus mimicking the natural protective mechanisms. The hypothesis will be tested initially in vitro in rat hepatoma cells and further evaluated in vivo in rats. The protective mechanism afforded by a low ALDH2 activity will be elicited by (i) orally-absorbable third generation antisense morpholino oligonucleotides directed against ALDH2 mRNA, and (ii) short interference RNAi molecules blocking ALDH2 mRNA administered with long-lasting adenoviral vectors. The high-activity ADH protective mechanism will be mimicked by (iii) transduction of the human ADHIB*2 gene and overexpression of the rat Adh with adenoviral vectors. As a 'proof of principle' we will (iv) determine the ability of single-point mismatched oligodeoxynucleotides to generate the Glu486Lys dominant-negative point mutation of ALDH2*2 in human hepatoma cells that carry the ADH gene, thus generating new cell lines that produce high levels of acetaldehyde. Overall, the proposed studies aim at inducing gene-based protective mechanisms that are specific and could be used for the treatment of alcoholism.